JPS5837342A - Reduction of imbalance moment in diesel main engine - Google Patents

Abstract

PURPOSE:To reduce vertical imbalance secondary moment possessed by a Diesel main engine by arranging at unequal angles the crank angle of the Diesel main engine in which the mass of each cylinder and the distance between the cylinders are equal. CONSTITUTION:In the case of a 6-cylinder main engine, on the basis of No.1 cylinder, for example, the angle to No.5 cylinder is set at 53 deg., the angle to No.3 cylinder at 134 deg., the angle to No.4 cylinder at 177 deg., the angle to No.2 cylinder at 263 deg., and the angle to No.6 cylinder at 313 deg., and unequal ignition is made. By this, as the secondary component of vertical imbalance moment is reduced, imbalance moment by the vertical and horizontal components of each cylinder is increased. To reduce the imbalance moment, a counter weight is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing the unbalanced moment of a diesel main engine by reducing the excitation force of the diesel main engine itself.

The arrangement of cylinders in a diesel engine is shown in Figures 1 and 2. Focusing on an arbitrary cylinder, the mass Mc
The crankshaft (1) of the piston rotates N times per minute, and the piston head (2) of the mass MR similarly repeats vertical movement N times per minute.

Now considering the crankshaft (4), centrifugal force F is generated due to rotation, and this centrifugal force F is expressed as F==Mcγω2.

Here, r: eccentricity of the crankshaft (1) 2πN ω: angular velocity (rad/5ec), which is ω-60.

The vertical component of the above centrifugal force F is Fv as shown in Figure 3.
If one horizontal component is FH, these values change depending on the crank angle θ (however, the centrifugal force F itself is constant). Similarly, inertial force is also generated due to the reciprocating mass MR.

Now, when the vertical component Fv1 and the horizontal component FH are applied to all cylinders, the total force is the unbalanced force FVI, FH
I (this FVI, FHI has \mass Mc and MR
(including those by).

For example, in the case of a 4-cylinder, /161 to /I6 at 90 degree pitch
As is clear from Fig. 4, if 4 cylinders are arranged,
The unbalanced forces FVI and FHI become zero. That is, vertical unbalanced force ΣFv-F, -F3=Q horizontal unbalanced force ΣFH=F2-P4=.

The second-order component Fv2 of this unbalanced force is a force generated at a repetition rate twice the number of rotations, and can be calculated using the same method as described above. However, the second-order component FV2 is induced only by the reciprocating quality i MR.

Next, unbalanced moments) MVI and MHI are obtained by multiplying the vertical component Fv1 of each cylinder by the horizontal component FH by the distance from the center of the main engine, which is the total for all cylinders.

Now, taking the case of a two-cylinder engine as an example, as shown in Fig. 5, the explanation is the moment that causes the main engine to rotate around its center. In FIG. 5, F is the distance to the rotating mass or restoring mass.

In the case of FIG. 5, it goes without saying that the unbalanced forces Fv and FH are zero.

MV2, which is the problem in this application, is the second-order component of the vertical unbalance moment, and is obtained by applying a lever to the second-order component of the unbalance force, 1"V2. As shown in Fig. 3) Provides rotational force to the main engine (4) installed above.

The second-order component MV2 of the vertical unbalance moment is a vibration source with a frequency twice the rotation speed, and in a low-speed diesel (for example, an RLA engine), it is usually 9077771 x 2 = 1800p.
It is about m. This is approximately in the same range as the vertical natural frequency of nodes 5 and 6 of the hull (the vertical natural frequency of nodes 5 and 6 depends on the ship type,
It varies depending on the size, but approximately 150 to 200 Cpm
). Therefore, if the value of the second-order component MV2 of the vertical unbalance moment is large, there is a possibility that resonance may occur and cause trouble.

Generally, when the unbalanced moment is large, a mechanical vibration damper is attached to the main engine or an electric vibration damper is installed at the stern, but these vibration dampers are very expensive. There are also ways to satisfy the unbalanced moment inside the main engine by changing the reciprocating mass or rotating mass for each cylinder, or by changing the cylinder spacing, but these methods are not preferred because they impair the compatibility of the main engine parts.

By the way, as mentioned above, the unbalanced force and the unbalanced moment are closely related to the arrangement angle (ignition angle) of the cylinder.

For example, in the four-cylinder example shown in Figure 1, if the arrangement of the /i62 cylinders is changed from a conformal arrangement to an unequal arrangement, the second-order component of vertical unbalance force F2V N horizontal unbalance force as shown in Figure 7. A 22nd-order formation F2H occurs, and the overall balance of 11 is lost.

Conversely, if the whole is not balanced, it is possible to reduce the total moment by adjusting the angle of the cylinder. Especially in the case of moment, since the lever factor is also included, the influence of angle changes is large. However, when one force or moment is decreased, another force or moment increases as a reaction. Therefore, it is desirable to reduce the second-order component MV2 of the vertical unbalance moment by allowing the increase, which is considered to have relatively little influence.

The present invention was developed in view of this point of view, and is characterized by arranging the crank angles of a diesel main engine at unequal angles in which each cylinder mass and cylinder spacing are equal, thereby reducing the vertical unbalance secondary moment of the main engine. That is.

Hereinafter, an embodiment of the present invention will be described in the case of a six-cylinder main engine.

Now, as shown in Figure 8 (a), the angle to the /165 cylinder is 53 degrees, the angle to the A63 cylinder is 134 degrees, the angle to the /164 cylinder is 177 degrees, and the angle to the /164 cylinder is 177 degrees, based on the /i61 cylinder. The angle of is 263 degrees, /1
Calculations were made for the case where unequal angle ignition was performed with the angle up to 66 cylinders set at 313 degrees. At that time, the unbalanced moment (unbalanced moment) in each cylinder of MV2 was as shown in the graph of Figure 8 (middle), and the unbalanced force and unbalanced moment were numerical values as shown in the table.

Also, counter weight CwFIT is installed on the /I61 cylinder side.
Attach ON and counterweight C to the /I66 cylinder side.
The unbalanced moment when WAI TON was attached was as shown in the table.

On the other hand, as shown in Figure 9, the angle to the rotary 5 cylinder is 60 degrees, the angle to the rotary 3 cylinder is 120 degrees, and the angle to the /I64 cylinder is 180 degrees, based on the /16.1 cylinder. Calculations were made for the case where equiangular ignition is performed with the angle up to the 2nd cylinder being 240 degrees and the angle up to the 6th cylinder being 300 degrees.

At that time, the magnitude of unbalanced moment (MV2) in each cylinder was as shown in the graph of FIG. 8 (b), and the unbalanced force and unbalanced moment were as shown in the table.

As the external unbalance moment MV2 decreases, the external unbalance moment MVI, MHI
increases, but in order to reduce this it is necessary to equip a counterweight. Here, the external unbalanced moment is the rotational moment transmitted to the hull (external) via the main engine stand, and the main engine itself is assumed to be rigid. Also, the internal unbalanced moment is the moment generated on the crankshaft itself due to the difference in the magnitude and direction of centrifugal force between adjacent cylinders, and this moment is not directly transmitted to the hull.

2 of the vertical unbalance moments that are directly related to the hull vibration
Focusing on the following components, in the case of anisotropic ignition, the percentage of isometric ignition is
It is possible to do the following.

Incidentally, the angle of the axonometric ignition of the present invention is not limited to the above-mentioned embodiments, and various angles may be selected, and other various changes may be made within the scope of the gist of the present invention. , etc., of course.

According to the method of reducing the unbalanced moment of a diesel main engine according to the present invention, the crank angles are arranged at unequal angles, and the mass of each cylinder and cylinder elevation are the same, so the compatibility of the engine parts is not compromised, and the existing diesel It can be easily applied to the main engine.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the arrangement of cylinders in a diesel engine, Figure 2 is an explanatory diagram of how the diesel engine cylinders rise and fall, and Figure 3 is an explanatory diagram of the centrifugal force generated by the rotating mass, as well as its vertical and horizontal components. , Fig. 4 is an explanatory diagram of the vertical unbalanced force and horizontal unbalanced force in the case of a 4-cylinder engine, Fig. 5 is an explanatory diagram of the unbalanced moment generated in the main engine, and Fig. 6 is an explanatory diagram of the unbalanced moment acting on the main engine. An explanatory diagram showing the situation. Figure 7 is an explanatory diagram when vertical unbalanced force and horizontal unbalanced force occur in the case of 4 cylinders. Figure 8 (f') is an explanatory diagram of the cylinder arrangement in the case of asymmetric ignition. Theory 1iIJ diagram, Figure 8 (b) is a graph showing the unbalanced moment in each cylinder in the case of anisotropic ignition), and Figure 9 (a) is a graph showing the size of My2, and Figure 9 (a) is the cylinder arrangement in the case of isometric ignition. The explanatory diagram, FIG. 9(0), is a graph showing the magnitude of the unbalanced moment M2 in each cylinder in the case of conformal ignition. In the figure, (1) is the crankshaft', (21 is the piston head,
(3) shows the hull, and (4) shows the main engine. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd. Figure 4 Figure 6

Claims (1)

[Claims] ]) A method for reducing the unbalanced moment of a diesel main engine, which is characterized by arranging the crank angles of diesel main engines with equal cylinder masses and equal cylinder intervals to reduce the vertical unbalanced second moment of the main engine.